1. Field of the Invention
This invention relates to a hammer device for an electronic keyboard instrument, which is applied to an electronic keyboard instrument, such as an electronic piano, and includes hammers each configured to pivotally move in accordance with key depression of an associated key.
2. Description of the Related Art
Conventionally, as a hammer device of the above-mentioned type, there has been known one proposed by the present assignee e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 2010-262129. This hammer device is applied to a keyboard device for an electronic piano. The hammer device is comprised of an action chassis formed by metal extrusion, and a plurality of hammers pivotally supported by the action chassis and arranged side by side in a left-right direction. The action chassis is comprised of a hammer supporting part having a fulcrum shaft portion extending in the left-right direction, and a switch mounting part provided in an upper portion of the hammer supporting part in a manner extending obliquely forward and upward from the hammer supporting part. A key switch for detecting key depression information on an associated key is mounted to the switch mounting part. The key switch is comprised of a switch board formed by a printed circuit board, and a plurality of switch bodies each formed by a rubber switch and provided on the lower surface of the switch board in association with the respective hammers.
The hammers are provided for respective keys, and each of the hammers is comprised of an arm-like hammer body extending in a front-rear direction and a weight attached to the front end of the hammer body. The hammer body has a rear end thereof formed with a shaft hole having a C shape in side view. The shaft hole is disengageably engaged with the fulcrum shaft portion of the action chassis, whereby the hammer is supported by the action chassis in a vertically pivotable manner. Further, the upper portion of the hammer body immediately forward of the shaft hole is formed with an actuator portion for pressing the switch body of the key switch from below during key depression.
The keyboard device is comprised of a plurality of swingable keys, and the hammers provided for the respective keys and each configured to pivotally move in accordance with key depression of an associated key. Each of the keys is swingably supported by a balance pin erected near the center of the keyboard device in the front-rear direction. Each of the hammers is comprised of the arm-like hammer body extending in the front-rear direction and the weight attached to the front end of the hammer body, as described above. Further, the hammer is pivotally supported by the action chassis via a bearing in the rear end of the hammer, and is placed on the upper surface of the rear end of the associated key via a capstan screw screwed into the hammer from below at a predetermined location forward of the bearing.
Further, in the above-described keyboard device, the ratio between a length from the front end of a key to an associated balance pin (hereinafter referred to as “the key front portion length”) and a length from the balance pin to an associated capstan screw via which an associated hammer is in contact with the key (hereinafter referred to as “the key rear portion length”) is set to approximately 3:2.
Generally, an electronic piano is demanded to be made compact in the depth dimension, and hence the length of an entire key in the front-rear direction is set to be shorter than that in an acoustic grand piano (hereinafter simply referred to as “the grand piano”). Further, in the above-described keyboard device, the ratio between the key front portion length and the key rear portion length is set to approximately 3:2 as mentioned above, and therefore the key front portion length of the keyboard device is far shorter than that of the grand piano. For this reason, when an electronic piano provided with the above-described keyboard device is played on, the difference in load e.g. between depression of a portion of a key close to the front end thereof and depression of a portion of the key rearwardly remote from the front end is larger than when a grand piano is played on, which makes it impossible to obtain touch feeling sufficiently similar to that provided by the grand piano.
To solve this problem, it has recently been under study to increase the key front portion length of an electronic piano and reduce the key rear portion of the same so as to obtain touch feeling closely similar to that provided by the grand piano without increasing the depth dimension of the electronic piano, i.e. to dispose the balance pin more rearward than in the conventional keyboard device.
Further, as shown in FIG. 11, the hammer, denoted by reference numeral 101, is comprised of an arm-like hammer body 102 extending in the front-rear direction and a weight 103 attached to the front end of the hammer body 102. The hammer body 102 is formed of a synthetic resin, and the weight 103 is formed of a metal, such as iron, having a high specific gravity. The hammer body 102 has a rear end thereof formed with a shaft hole 104. The shaft hole 104 is engaged with a hammer fulcrum (not shown), whereby the hammer 101 is pivotally supported by the hammer fulcrum.
A capstan screw 105 is screwed into the lower surface of the hammer body 102 at a location forward of the shaft hole 104. The capstan screw 105 is held in contact with the rear end of the upper surface of a swingable key (not shown). Therefore, when the key is depressed, the rear portion of the key pivotally moves upward, and the hammer 101 is driven via the capstan screw 105 and pivotally moves upward about the hammer fulcrum. Further, in the hammer 101, the ratio between a distance LG0 from a center CH0 of the hammer fulcrum to a center of gravity GG0 of the weight 103 and a distance LD0 from the center CH0 of the hammer fulcrum to a driving point PD0 via which the capstan screw 105 is in contact with the key is set to approximately 3.7:1.
In general, in the hammer device constructed as above, grease or the like is applied as a lubricant to the entire fulcrum shaft portion of the action chassis so as to ensure smooth pivotal motion of each hammer. When a hammer is dismounted from the action chassis e.g. for maintenance, after the maintenance operation, it is required to mount the hammer to the action chassis. However, when bringing the shaft hole of the hammer into engagement with the fulcrum shaft portion during the operation for mounting the hammer, the actuator portion of the hammer can be brought into contact with the fulcrum shaft portion, and hence in this case, there is a fear that the grease on the fulcrum shaft portion adheres to the actuator portion of the hammer. In such a case, if the hammer is mounted to the action chassis with the grease adhering to the actuator portion, the following problem will occur:
During playing on the electronic piano, a hammer associated with a depressed key pivotally moves upward to press an associated switch body by the actuator portion thereof, and then when the key is released, the hammer pivotally moves downward and returns to its original key-released state. During this process, however, when the actuator portion of the hammer is departing from the switch body being pressed by the actuator portion, the switch body made of rubber is slightly pulled toward the actuator portion by adhesion of the grease adhering to the actuator portion, and consequently a noise is sometimes produced at the moment when the switch body and the actuator portion are separated from each other. This noise impairs performance played on the electronic piano. Of course, it is possible to avoid adhesion of grease to the actuator portion by mounting the hammer to the action chassis while taking care not to bring the actuator portion into contact with the fulcrum shaft portion. In this case, however, when it is required to mount a large number of hammers, the mounting operation takes much time and labor. Thus, the above-described keyboard device leaves room for improvement.
Further, assuming that the conventional hammer device is directly applied to a keyboard device in which each balance pin is positioned more rearward than it conventionally is, the following problem occurs: In a case where the balance pin is positioned close to the front end of an associated hammer, there is a fear that when the hammer having pivotally moved upward in accordance with key depression is returning to its original key-released state while pivotally moving downward, the hammer comes into abutment with the balance pin. In general, a hammer device for an electronic piano is configured such that each hammer can be dismounted from an action chassis that supports the hammers, e.g. for maintenance. In this case, although each key cannot be dismounted from the action chassis within a range of pivotal motion of an associated hammer which is performed in accordance with the motion of key, in a state where the key on which the hammer is placed via the capstan screw is dismounted from the keyboard device, by pivotally moving the hammer below its position in the key-released state, the hammer can be dismounted from the action chassis. However, in the case where the balance pin is positioned close to the front end of the hammer, when attempting to pivotally move the hammer downward lower than its position in the key-released state, the hammer is sometimes brought into abutment with the balance pin as described above, thereby hindering the hammer from being pivotally moved to a position where it can be dismounted. In this case, the hammer cannot be dismounted from the action chassis.
Further, in the conventional hammer, the ratio between the distance LG0 from the center CH0 of the hammer fulcrum to the center of gravity GG0 of the weight 103 and the distance LD0 from the center CH0 of the hammer fulcrum to the driving point PD0 of the capstan screw 105 is set to a relatively small ratio of approximately 3.7:1, as described hereinabove, which means that the distance LG0 is relatively short. On the other hand, the dynamic load (moment of inertia) of the hammer is approximately proportional to the square of the distance LG0. For this reason, even if the weight 103 is made heavier, the dynamic load increases less effectively than could be otherwise expected from the increase in the weight, and hence the dynamic load tends to be rather insufficient. As a consequence, only a dissatisfactory, light touch feeling can be obtained, and therefore the conventional hammer leaves room for improvement in this respect.